(1) Field of the Invention
The present invention relates to a welding process and apparatus. More particularly, the invention relates to a welding process and apparatus in which by applying a force acting in an optional direction to a molten metal pool by a shifting magnetic field, welding of various positions can be facilitated and the welding efficiency and the quality of weld metal can be improved.
(2) Description of the Prior Art
The easy or difficulty of a conventional welding operation is remarkably influenced by the welding position. In general, flat welding is easiest, but in case of horizontal fillet welding, horizontal welding, vertical upward welding, vertical downward welding and overhead welding, various limitations are added to conditions adopted in flat welding, and problems such as reduction of the welding speed, degradation of the quality of weld metal and reduction of the welding efficiency are brought about. Needless to say, these problems owing to the difference of the welding position are caused by gravity acting on the molten metal pool.
Various methods have heretofore been proposed for preventing sagging of a molten metal pool or controlling the shape of the molten metal pool.
For example, the specification of U.S. Pat. No. 3,584,181 (to Nemoto et al) proposes a submerged arc welding method for hard facing, in which a tape electrode is used and in order to prevent detrimental influences of a magnetic field formed around the electrode, a coil being disposed around a material to be welded to apply an additional magnetic field thereto and form a uniform surface built-up portion.
The specification of U.S. Pat. No. 3,701,881 (to Rother et al) discloses a method for welding thin metal sheets in which butt welding is made possible without use of foils or while eliminating the subsequent heat treatment, by shifting the arc from the position of a core of a welding torch relatively to the metal sheets by an action of a magnetic field.
The specification of U.S. Pat. No. 3,885,123 (to Sciaky et al) discloses a welding apparatus in which two welding torches are used and arcs of the two torches are brought close to each other by utilizing a magnetic field.
Further, the specification of U.S. Pat. No. 3,941,974 (to Kano et al) proposes a welding method for obtaining deep penetrations, in which the direction of the arc is controlled by a magnetic field generated by an auxiliary current.
Even according to these conventional techniques, however, the welding operation cannot be performed at a high efficiency in case of welding of difficult positions, for example, vertical welding, horizontal welding or overhead welding.